A Qatari sheikh who has reportedly spent more than $1.5 billion on his art collection has been accused in a London court of failing to honor a multi-million pound auction purchase and is being compared to an “inveterate gambler” who cannot stop bidding on antiques.

Sheikh Saud Bin Mohammed Al-Thani, once known as world’s largest art collector, has reportedly left a trail of an estimated $60-million debt to auction houses around the world.

The sheikh is being sued by dealers who say he has failed to pay up $19.7 million for a collection of ancient Greek coins sold at an auction in New York earlier this year, the Daily Mail reported.

He reportedly purchased nearly $20 million worth of coins from the Prospero Collection, regarded as the finest assortment of Archaic, Classical and Hellenistic Greek coins ever assembled, the dealers told the High Court in London, the Daily Mail reported.

Though the dealers are still in possession of the coins, they insist that the sheikh should be held accountable for his winning bid.

The dealers’ lawyer, Jeffrey Gruder, likened Saud to an “inveterate gambler” who had an uncontrollable desire to bid on works of art.

“He bids, wins and then doesn’t pay. One can only conclude that this is a person acting dishonorably and disreputably. He is bidding when he knows he’s not going to be able to pay,” the Daily Mail quoted Gruder as saying.

“Perhaps in a perverse way he enjoys the process of bidding,” he said.

Gruder alleged that Sheikh Saud’s total unpaid bill to worldwide auctioneers and art dealers include a $42 million debt owed to Sotheby’s and $6.5 million owed to Bonhams apart from sums owed to at least five other dealers.

The dealers have demanded freezing of the assets of the sheikh, a cousin of the ruling emir of Qatar.

Saud’s lawyer Stephen Rubin vehemently denied the claims calling them “obviously wrong” and has questioned the credibility of the lawsuit, saying the dealers had no “contract of sale” to produce against the sheikh.

Rubin said the sheikh had been “trying to pay” for the coins for the past nine months, adding, “there are no doubt timing issues which go to why he cannot pay at the moment, but that’s not a reason to make a freezing order against someone.”

Saud was once the chairman of Qatar’s National Council for Culture, Arts and Heritage but was removed from his position in March 2005. Though no official reason was given for Saud’s removal, there have been reports that the emir was unhappy with his cousin who didn’t demarcate between works of art bought for himself and for Doha’s museums, which pointed to the possibility of Saud’s misuse of public funds.